Digital Control of Terrace Width of One-dimensional Semiconductor Surfaces by Modification of Lattice Strain

清洁的Si（110）表面呈现“16 × 2”重构，其中一维上下台阶交替排列。平台宽度约为2.5 nm，相邻平台之间的高度差为一个原子层，0.2 nm。这种表面是一个有前途的基板，为未来的低维电子器件以及纳米生物材料。在这项研究中，我们试图通过一种独特的方法，利用金属吸附控制梯田宽度。这是基于这样的想法，即表面应力起着决定表面台阶密度的作用。我们使用的金属是锡，它与硅属于相同的周期表，因为同质掺杂对表面的电子结构没有太大影响。在0.2 ML的Sn吸附在表面上，16 × 2变成28 × 2，这是由低能电子衍射以及扫描隧道显微镜证实。STM观察表明，锡原子形成三聚体，并相应地插入到硅的五角簇中。结果，表面应力降低，使梯田宽度扩大到50%左右。除了结构的观点外，我们还尝试用氢终止技术来改变上下台阶的电子性质。结果表明，在反应初期，氢原子与五边形团簇中的特定原子发生反应，降低了表面应力，且上下结构保持氢原子的饱和覆盖，显示了该表面即使在空气中也具有潜在的应力。Si（110）上的Ag和Ba沉积正在进行中

The clean Si (110) surface shows a "16x2" reconstruction, where one-dimensional up-and-down terraces arrange alternatively. The terrace width is about 2.5 nm and the height difference between the adjacent terraces is one atomic layer, 0.2 nm. This surface is a promising substrate for future low-dimensional electronic devices as well as nano-biomaterials. In this study, we have tried to control the terrace width by a unique method using metal adsorption. This is based on the idea that the surface stress plays a role to determine the surface step density. The metal we used is a tin, which belongs the same periodic table as silicon, because homovalent doping does not so much affect electronic structures on the surface. At 0.2 ML adsorption of Sn on the surface, the 16x2 changed into 28x2, which was confirmed by low-energy electron diffraction as well as scanning tunneling microscopy. STM observation shows that Sn atoms forms trimers which are inserted accordingly into the silicon pentagonal clusters. As a result, surface stress was reduced to make the terrace width being enlarged to about 50%. In addition of structural point of view, we attempted to modify electronic nature of the up-and-down terraces by hydrogen termination technique. The result shows that, at the initial stage of reaction, atomic hydrogen reacts with specific atoms in pentagonal cluster to reduce surface stress, and that the up-and-down structure is kept at a saturation coverage of hydrogen, demonstrating the potential of this surface even in air. Ag and Ba deposition on Si(110) are now in progress